A frontal paranasal sinus mucocoele (pronounced 'myü-k&-"sEl) is a cystic lesion full of thick mucous in the paranasal sinuses. It develops when the opening of a paranasal sinus becomes obstructed because of trauma, infection, chronic sinusitis, polyps, malignancy, bony tumors, or congenital anomalies. As it increases in size, a mucocoele can make its way through the surrounding bone or discharge through the skin.
The majority of paranasal sinus mucocoeles are frontal sinus mucocoeles. They are generally benign but if they expand the pressure they exert on the surrounding areas can cause problems.
Mucocoeles tend to expand to where there is least resistance, often through the thin bone of the superior orbital wall. If a mucocoele becomes infected, it can form epidural abscesses, meningitis, subdural empyema (pus), or intracerebral abscesses.
The preferred imaging method for paranasal sinus pathology is a computed tomography (CT) scan. A CT scan will show a mucocoele as an expanded, airless sinus filled with homogeneous material. The walls of the sinus may appear normal or may show thickening, thinning and erosion to various degrees.
If there is intracranial extension or infection, magnetic resonance imaging (MRI) may be used. On an MRI, the mucoid contents of the mucocoele will appear distinctly and diffusely.
Management of mucocoeles depends on the size and the pressure effects they are having. In the case of small mucocoeles, medical management with decongestants and steroids can be effective. Large mucocoeles causing pressure problems might require surgical intervention to reestablish adequate drainage of the sinus. This may be achieved through open surgical or endoscopic techniques.
